The visual environment contains more information than can be processed simultaneously. Due to this limited processing capacity of the visual system, it is necessary to select the behaviorally most relevant information for further processing and to filter out the unwanted information, a fundamental ability known as attentional selection. There is converging evidence from physiology studies in monkeys and neuroimaging studies in humans that attentional selection occurs at multiple stages along the visual pathway and is controlled by a network of higher-order areas in frontal and parietal cortex that includes the frontal eye fields (FEF) and the lateral intraparietal area (LIP) in the monkey and functionall similar areas in the human. In monkeys, physiology studies have begun to characterize the interactions across the network by simultaneously recording from two or more interconnected nodes of the attention network. One important result of these studies suggests that the strength of attentional modulation depends on the degree of neural synchrony between areas. In contrast, in humans, little is known about the temporal dynamics and functional interactions across areas of the attention network. Further, despite the macaque brain serving as prime model for a basic understanding of human brain function, it remains unclear how neural mechanisms related to perception and cognition compare across primate species. By recording intracranially from frontal and parietal cortex of monkeys and of epilepsy patients, who are chronically implanted with subdural grids for diagnostic purposes, while performing an identical spatial attention task we pursue two main goals in this project: (i) to characterize the temporal dynamics of the human attention network; and (ii) to compare electrophysiological signals related to spatial attention and obtained in functionally similar areas across primate species (monkey/human). The central hypothesis is that modulation of oscillatory activity plays an important functional role in spatial attention control and can predict behavioral outcome in both primate species. The significance of the proposed research is that it will contribute to our understanding of a fundamental cognitive operation, selective attention, the impairment of which has devastating consequences on human health. Attentional deficits are frequently observed in neurological diseases, e.g. after stroke, leading to visuo-spatial neglect, an impairment in directing attention to contralesional visual space, as well as in psychiatric diseases (e.g. schizophrenia). In addition, our proposed studies will be the first to directly compare human and macaque physiology, thereby connecting two different bodies of literature, i.e. EEG/fMRI and macaque electrophysiology.